Use of a copper zinc alloy

ABSTRACT

A copper zinc alloy that is used as a material for a sliding bearing wherein the alloy comprises 59-73% copper, 2.7-8.5% manganese, 1.5-6.3% aluminum, 0.2-4% silicon, 0.2-3% iron, 0-2% lead, 0-2% nickel, 0-0.4% tin, residual zinc and unavoidable impurities.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of PCT/EP2006/002945;filed Mar. 31, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a copper zinc alloy, which is employable forsliding bearings.

2. Discussion of the Prior Art

Among the requirements for a material that is intended to be used as asliding bearing, the material must possess a low friction coefficient inorder to avoid “jamming” and a high wear resistance in order to obtain along service life. For a sliding bearing in an internal combustionengine, there are currently used copper zinc alloys of the typeCuZn31Si1. However, the properties of the CuZn31Si1 alloys no longermeet the requirements that are imposed on materials for sliding bearingsin modern engines, for instance, diesel engines. In such diesel engines,the operating temperature of the sliding bearings may reach and exceed300° C. The employed copper zinc alloys; however, soften at temperaturesaround 250° C. Consequently, sliding bearings made of this alloy nolonger have the requisite strength at the operating temperature.

In recognition of these circumstances, the invention is therefore basedon the problem of providing a copper zinc alloy for use as a materialfor sliding bearings, wherein the copper zinc alloy meets therequirements imposed on a material for sliding bearings, in particularat elevated temperatures, and can also be easily produced.

SUMMARY OF THE INVENTION

The object is achieved according to the invention by the use of a copperzinc alloy as a material for sliding bearings wherein the alloycomprises 59-73% copper, 2.7-8.5% manganese, 1.5-6.3% aluminum, 0.2-4%silicon, 0.2-3% iron, 0-2% lead, 0-2% nickel, 0-0.4% tin, residual zincand unavoidable impurities.

The figures given in percent relate here and hereafter to percent byweight.

Consequently, a novel use for a copper zinc alloy is thereforespecified. A similar alloy according to DE 29 19 478 C2 is used as asynchronizing ring alloy and is known to those skilled in the artbecause of this field of use as an alloy, which has a high frictioncoefficient in combination with the other intrinsic material properties.However, a high friction coefficient is disadvantageous for the use of amaterial as a sliding bearing, since a high friction coefficientdescribes a strong interaction between the sliding bearing and itssurroundings and is also expressed by a great tendency to jam during thesliding operation. Therefore, the material claimed for the novel use asa sliding bearing has not previously been considered as a slidingbearing material. In relation to the friction coefficient of thepreviously used CuZn31Si1 alloys, however, the friction coefficient ofthe claimed copper zinc alloy is lower than that of known slidingbearing materials. This is completely surprising and contrary to the“high” friction coefficient familiar to a person skilled in the art andwell established for a synchronizing ring alloy.

Apart from the low friction coefficient and a good wear resistance, ithas been found that the claimed copper zinc alloy has a surprisinglygood thermal stability. This unexpected combination of materialproperties makes use as a material for sliding bearings possible for thefirst time.

The requirement that it can be produced well and easily is satisfied byit being possible for the material for sliding bearings to be producedin bar form by semicontinuous or fully continuous casting, extruding anddrawing, that is to say by hot and cold forming.

DETAILED DESCRIPTION OF THE INVENTION

The alloy has a microstructure which comprises an alpha mixed crystalcomponent and a beta mixed crystal component.

In an advantageous development, the copper zinc alloy for use as amaterial for sliding bearings comprises 68-72.5% copper, 5.8-8.5%manganese, 3.6-6.3% aluminum, 0.5-3.3% silicon, 0.2-2.5% iron, 0.2-1.9%lead, 0-1.5% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

The microstructure of the developed alloy produced according to DE 29 19478 C2 comprises an alpha and beta mixed crystal matrix with up to60-85% alpha phase. The microstructure also includes hard intermetalliccompounds, for example iron-manganese silicides. The alpha phase isdecisive for the thermal stability of the alloy.

Sliding bearings of this alloy have a particularly high wear resistance,which is even much higher than that of the alloy CuZn31Si1. The low dryfrictional wear in the case of sliding bearings of said alloy results inbetter behavior under inadequate lubricating conditions. Consequently,the high wear resistance also ensures the emergency running propertiesof a sliding bearing. The wear-reducing effect is particularlyadvantageous especially at temperatures around 300° C., the operatingtemperature of the sliding bearings in modern engines.

In comparison with the previously used CuZn31Si1 alloys, the novelclaimed sliding bearing material has a lower jamming tendency, which isattributable to the significantly reduced friction coefficient.

In a preferred alternative, the use is claimed of a copper zinc alloywherein the alloy comprises 68.9-71.4% copper, 6.9-8.5% manganese,4.3-6% aluminum, 1.1-2.6% silicon, 0.4-1.9% iron, 0.3-1.6% lead, 0-0.8%nickel, 0-0.4% tin, residual zinc and unavoidable impurities.

The microstructure of the alloy produced in the customary way has analpha and beta crystal matrix with up to 80% distributed alpha phase.Hard intermetallic compounds, for example iron-manganese silicides, areadditionally contained.

It is advantageous for the use of this alloy as a material for slidingbearings that there is a stable high hardness level in the desiredoperating range above 300° C., and the softening of the alloy onlybegins well over 100 K above the softening temperature of currently usedCuZn31Si1 alloys.

Advantageously used as a material for sliding bearings is a copper zincalloy wherein the alloy comprises 69.5-70.5% copper, 7.4-8.1% manganese,4.8-5.7% aluminum, 1.5-2.2% silicon, 0.8-1.4% iron, 0.4-1.2% lead,0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidable impurities.

The microstructure of said, correspondingly produced alloy has a matrixof beta mixed crystals in which alpha deposits are embedded. Alsocontained in the microstructure are likewise randomly dispersedmanganese-iron silicides. Apart from a low friction coefficient and ahigh wear resistance, this alloy has a high softening temperature.

In a preferred alternative, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 69.4-71.4% copper,7.4-8.1% manganese, 4.8-5.7% aluminum, 1.7-2.2% silicon, 0.8-1.4% iron,0.4-1.2% lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

Sliding bearings of this alloy have a particularly high wear resistance.The low dry frictional wear in the case of sliding bearings of saidalloy results in better behavior under inadequate lubricatingconditions. Consequently, the high wear resistance also ensures theemergency running properties of a sliding bearing. The wear-reducingeffect is particularly advantageous especially at temperatures around300° C., the operating temperature of the sliding bearings in modernengines.

Intermetallic compounds, in particular iron-manganese silicides,determine the high wear resistance the wear resistance increasing withan increasing proportion of intermetallic compounds in the alloy. A highproportion of intermetallic compounds are brought about by a highproportion of Si, a high proportion of the α phase, for the thermalstability of the alloy, being ensured by the high Cu content with theiron and manganese contents remaining the same.

In a further embodiment, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises more than 70 and up to71.4% copper, 7.4-8.1% manganese, 4.8-5.7% aluminum, 1.8-2.2% silicon,0.8-1.4% iron, 0.4-1.2% lead, 0-0.3% nickel, 0-0.4% tin, residual zincand unavoidable impurities.

Sliding bearings of this alloy have a particularly high wear resistance.The low dry frictional wear in the case of sliding bearings of saidalloy results in better behavior under inadequate lubricatingconditions. Consequently, the high wear resistance also ensures theemergency running properties of a sliding bearing. The wear-reducingeffect is particularly advantageous especially at temperatures around300° C., the operating temperature of the sliding bearings in modernengines.

Intermetallic compounds, in particular iron-manganese silicides,determine the high wear resistance the wear resistance increasing withan increasing proportion of intermetallic compounds in the alloy. A highproportion of intermetallic compounds are brought about by a highproportion of Si, a high proportion of the α phase, for the thermalstability of the alloy, being ensured by the high Cu content with theiron and manganese contents remaining the same.

In a preferred alternative, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 63.5-67.5% copper, 6-8.5%manganese, 3.6-6.3% aluminum, 0.5-3% silicon, 0.2-2.5% iron, 0.02-1.8%lead, 0-1.5% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

The microstructure of the developed alloy produced according to DE 29 19478 C2 comprises an alpha and beta mixed crystal matrix with up to60-85% alpha phase. The microstructure also includes hard intermetalliccompounds, for example iron-manganese silicides. The alpha phase isdecisive for the thermal stability of the alloy.

Suitability for use as a material for sliding bearings in modern enginesrequires the combination of high thermal stability above 300° C. withgood wear resistance, which is necessary because of the sliding of acomponent produced from such materials. In addition, a low frictioncoefficient is required, by which the slidability of a componentproduced from such material is improved.

The use of said alloy for sliding bearings is particularly advantageous,since it has a much improved wear behavior in comparison with thepreviously used copper zinc alloys, and consequently also ensures theemergency running properties of a sliding bearing.

In a further refinement, the use is claimed of a copper zinc alloywherein the alloy comprises 64.5-66.5% copper, 6.9-8.5% manganese,4.3-6% aluminum, 0.9-2.6% silicon, 0.4-1.9% iron, 0.1-1.3% lead, 0-0.8%nickel, 0-0.4% tin, residual zinc and unavoidable impurities.

The microstructure of the alloy produced in the customary way has analpha and beta crystal matrix with up to 80% distributed alpha phase.Hard intermetallic compounds, for example iron-manganese silicides, areadditionally contained.

It is advantageous for the use of this alloy as a material for slidingbearings that there is a stable high hardness level in the desiredoperating range above 300° C., and the softening of the alloy onlybegins well over 100 K above the softening temperature of currently usedCuZn31Si1 alloys.

In a further embodiment, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 65.1-66% copper, 7.4-8.1%manganese, 4.8-5.7% aluminum, 1.3-2% silicon, 0.8-1.4% iron, 0.2-0.9%lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

The microstructure of said, correspondingly produced alloy has a matrixof beta mixed crystals with alpha deposits. Randomly dispersediron-manganese silicides are contained in the microstructure.

Apart from a low friction coefficient and a high wear resistance, thisalloy also has a high softening temperature.

In a preferred alternative, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 65.1-66% copper, 7.4-8.1%manganese, 4.8-5.7% aluminum, 1.7-2% silicon, 0.8-1.4% iron, 0.2-0.9%lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

The use of said alloy for sliding bearings is particularly advantageous,since it has a much improved wear behavior in comparison with thepreviously used copper zinc alloys, and consequently also ensures theemergency running properties of a sliding bearing.

Intermetallic compounds, in particular iron-manganese silicides,determine the high wear resistance. The wear resistance increases withan increasing proportion of intermetallic compounds in the alloy. A highproportion of intermetallic compounds are brought about by a highproportion of Si.

In a further embodiment, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 65.1-66% copper, 7.4-8.1%manganese, 4.8-5.7% aluminum, 1.8-2% silicon, 0.8-1.4% iron, 0.2-0.9%lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

The use of said alloy for sliding bearings is particularly advantageous,since it has a much improved wear behavior in comparison with thepreviously used copper zinc alloys, and consequently also ensures theemergency running properties of a sliding bearing.

The high wear resistance is determined by intermetallic compounds, inparticular iron-manganese silicides. The wear resistance increases withan increasing proportion of intermetallic compounds in the alloy. A highproportion of intermetallic compounds are brought about by a highproportion of Si.

In a preferred alternative, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 68.3-72.7% copper,5.7-8.5% manganese, 3.6-6.3% aluminum, 0.5-3.3% silicon, 0.2-2.5% iron,0-0.1% lead, 0-1.5% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

This alloy has the particular property that, because of the low leadcontent, it counts as a lead-free alloy and therefore represents amaterial for sliding bearings that also satisfies the environmentalaspect gaining increasing importance in engine construction. Inaddition, the combination of the properties of this alloy that isimportant for sliding bearings exceeds the properties of known slidingbearing materials.

The microstructure of the developed alloy produced according to DE 29 19478 C2 comprises an alpha and beta mixed crystal matrix with up to60-85% alpha phase. The microstructure also includes hard intermetalliccompounds, for example iron-manganese silicides. The alpha phase isdecisive for the thermal stability of the alloy.

Sliding bearings of this alloy have a particularly high wear resistance,which is even much higher than that of the alloy CuZn31Si1. The low dryfrictional wear in the case of sliding bearings of said alloy results inbetter behavior under inadequate lubricating conditions. Consequently,the high wear resistance also ensures the emergency running propertiesof a sliding bearing. The wear-reducing effect is particularlyadvantageous especially at temperatures around 300° C., the operatingtemperature of the sliding bearings in modern engines.

In comparison with the previously used CuZn31Si1 alloys, the novelclaimed sliding bearing material has a lower jamming tendency, which isattributable to the significantly reduced friction coefficient.

In a further refinement, the use is claimed of a copper zinc alloywherein the alloy comprises 69.4-71.6% copper, 6.9-8.5% manganese,4.3-6% aluminum, 1.1-2.6% silicon, 0.4-1.9% iron, 0-0.1% lead, 0-0.8%nickel, 0-0.4% tin, residual zinc and unavoidable impurities.

The microstructure of the alloy produced in the customary way has analpha and beta crystal matrix with up to 80% alpha phase. Hardintermetallic compounds, for example iron-manganese silicides, areadditionally contained.

Advantageous for the use of this lead-free and consequentlyenvironmentally compatible alloy as a material for sliding bearings isthat there is a high hardness level in the desired operating range above300° C., and the softening of the alloy only begins above the softeningtemperature of currently used CuZn31Si1 alloys.

In a further embodiment, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 70-71% copper, 7.4-8.1%manganese, 4.8-5.7% aluminum, 1.5-2.2% silicon, 0.8-1.4% iron, 0-0.1%lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

The microstructure of said, correspondingly produced alloy has an alphaand beta mixed crystal matrix. Likewise randomly dispersedmanganese-iron silicides are contained in the microstructure.

Apart from a low friction coefficient and an improved wear resistance,this lead-free, environmentally compatible alloy also has a highersoftening temperature.

In a preferred alternative, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises 69.4-71.4% copper,7.4-8.1% manganese, 4.8-5.7% aluminum, 1.7-2.2% silicon, 0.8-1.4% iron,0-0.1% lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.

Sliding bearings of this alloy have a particularly high wear resistance.The low dry frictional wear in the case of sliding bearings of saidalloy results in better behavior under inadequate lubricatingconditions. Consequently, the high wear resistance also ensures theemergency running properties of a sliding bearing. The wear-reducingeffect is particularly advantageous especially at temperatures around300° C., the operating temperature of the sliding bearings in modernengines.

The high wear resistance is determined by intermetallic compounds, inparticular iron-manganese silicides, the wear resistance increasing withan increasing proportion of intermetallic compounds in the alloy. A highproportion of intermetallic compounds is brought about by a highproportion of Si, a high proportion of the □ phase, for the thermalstability, being ensured by the high Cu content.

In a further embodiment, used as a material for sliding bearings is acopper zinc alloy wherein the alloy comprises more than 70 and up to71.4% copper, 7.4-8.1% manganese, 4.8-5.7% aluminum, 1.8-2.2% silicon,0.8-1.4% iron, 0-0.1% lead, 0-0.3% nickel, 0-0.4% tin, residual zinc andunavoidable impurities.

Sliding bearings of this alloy have a particularly high wear resistance.The low dry frictional wear in the case of sliding bearings of saidalloy results in better behavior under inadequate lubricatingconditions. Consequently, the high wear resistance also ensures theemergency running properties of a sliding bearing. The wear-reducingeffect is particularly advantageous especially at temperatures around300° C., the operating temperature of the sliding bearings in modernengines.

The high wear resistance is determined by intermetallic compounds, inparticular iron-manganese silicides, the wear resistance increasing withan increasing proportion of intermetallic compounds in the alloy. A highproportion of intermetallic compounds are brought about by a highproportion of Si, a high proportion of the □ phase, for the thermalstability of the alloy, being ensured by the high Cu content with theiron and manganese contents remaining the same.

Used in an expedient way, as a material for sliding bearings is a copperzinc alloy wherein the alloy additionally comprises at least one of theelements chromium, vanadium, titanium or zirconium with up to 0.1%.

The addition of these elements to the copper zinc alloy has the effectof making the grains finer.

In addition, when used for a sliding bearing, the copper zinc alloy maycomprise at least one of the following elements with a concentration≦0.0005% boron, ≦0.03% antimony, ≦0.03% phosphorus, <0.03% cadmium,≦0.05% chromium, ≦0.05% titanium, ≦0.05% zirconium and ≦0.05% cobalt.

A number of exemplary embodiments are explained in more detail on thebasis of the following description and on the basis of Table 1.

Currently used as a material for sliding bearings that are subjected tomoderate thermal stress are copper zinc alloys of the CuZn31Si1 typewith approximately the following composition: 68% copper, 1% silicon,0.3% lead and residual zinc. This alloy is referred to hereafter as thestandard alloy. Alloy 1 corresponds to the alloy from claim 4 and has acomposition of 70% copper, 7.7% manganese, 5.2% aluminum, 1.8% silicon,1.1% iron, 0.8% lead, residual zinc and unavoidable impurities. Alloy 2corresponds to the alloy from claim 9 and has a composition of 65.5%copper, 7.7% manganese, 5.2% aluminum, 1.6% silicon, 1% iron, 0.5% lead,0.1% nickel, 0.2% tin, residual zinc along with unavoidable impurities.Alloy 3 corresponds to the alloy from claim 14 and has a compositionwith 70.5% copper, 7.7% manganese, 5.2% aluminum, 1.8% silicon, 1.1%iron, 0.05% lead, 0.1% nickel, 0.2% tin, residual zinc and unavoidableimpurities.

The softening behavior of the various materials has been investigated upto a temperature of 600° C. This showed that the hardness of thestandard alloy for sliding bearings falls significantly from atemperature as low as 250° C. and, at 400° C., is only 130 HV50, thefall in the hardness progressing continuously with increasingtemperature. By contrast with this, no reduction in hardness wasmeasured for alloy 1 in the temperature range between 200 and 450° C.Only after 450° C. does the hardness of alloy 1 also fall as thetemperature increases further. Alloy 3 likewise shows a constanthardness value from 250 to 430° C. The stable hardness value of alloy 3therefore extends beyond the range in which the standard alloy alreadydisplays significant losses in hardness. The progression of the hardnessvalues of alloy 2 is comparable to the hardness progression of thestandard alloy, but alloy 2 has a much higher hardness.

Consequently, alloys 1 and 3, and to some extent alloy 2, have theirmaximum hardness at the temperatures that correspond to the operatingtemperature of sliding bearings in modern engines.

The electrical conductivity can be used as a measure of the thermalconductivity, a high value standing for good thermal conductivity. Thestandard alloy has an electrical conductivity of 8.2 m/Ωmm². Theelectrical conductivity of alloys 1, 2 and 3 is lower than that of thestandard alloy at 4.6 m/Ωmm², 4 m/Ωmm² and 5.4 m/Ωmm², respectively.This means that the heat dissipation of alloys 1, 2 and 3 is reduced incomparison with the standard alloy. However, as a result of theotherwise superior properties, this is acceptable.

The wear behavior was investigated with and without a lubricant. Withlubricant, alloy 3 has the highest wear resistance (1250 km/g). Alloy 1has a likewise outstanding wear resistance of 961 km/g, which arevirtually two orders of magnitude higher than the wear resistance of thestandard alloy at 12 km/g. At 568 km/g, the wear resistance of alloy 2exceeds the wear resistance of the standard alloy by approximately oneand a half orders of magnitude.

In investigations of the wear behavior without lubricant, it has beenfound by way of confirmation that alloys 1 and 3 have distinctadvantages over the standard alloy. The wear of the standard alloy is357 km/g, whereas the wear of the two alloys 1 and 3 is in each case1250 km/g. The wear resistance is consequently in each case higher by afactor of three than the wear resistance of the standard alloy. In otherwords, the wear is much less. Alloy 2 has slightly greater wear that thestandard alloy of 417 km/g.

Alloys 1, 2 and 3 can be produced with preference by semicontinuous orfully continuous casting, extruding, drawing and straightening.

A friction coefficient of 0.29, such as that of the standard alloy, hasuntil now been considered to be a low friction coefficient, andconsequently the material of the type CuZn31Si1 has been considered tobe an ideal sliding bearing material. Alloys 1, 2 and 3, which haveuntil now been used as synchronizing ring material—requiring a highfriction coefficient—show that, surprisingly, the friction coefficientclassified as high for this known use is actually low. For instance, at0.14, the friction coefficient of alloy 2 is only half the frictioncoefficient of the standard alloy, classified until now as low. Alloys 1and 3 even exhibit friction coefficients of 0.10 and 0.11, respectively,which are only one third of the low friction coefficient of the standardalloy. Consequently, alloys 1, 2 and 3 are surprisingly suitable for useas a sliding bearing material that has much improved sliding propertieson account of the low friction value.

Alloys 1, 2 and 3 have distinct advantages over the standard alloy useduntil now for sliding bearings. These advantages concern, inter alia,the softening temperature, the sliding properties and the wearresistance. In addition, the conductivity is also adequate.Consequently, alloys 1, 2 and 3 represent a considerable improvementwith respect to use as a sliding bearing material. These alloys meet therequirements imposed on the material because of the increased operatingtemperatures in modern diesel engines.

Table 1 shows the material properties of a standard copper zinc alloyand of alloy 1, alloy 2 and alloy 3 in comparison.

Standard Property alloy Alloy 1 Alloy 2 Alloy 3 Electrical 8.2 4.6 4.05.4 conductivity (m/Ωmm²) Wear, dry (km/g) 357 1250 417 1250 Wear,lubricated 12 961 568 1250 (km/g) Softening 350 480 370 480 temperature10% cold-worked (° C.) Friction value 0.29 0.10 0.14 0.11

Having properties comparable to those of alloy 1 is the following alloy:70.2% copper, 7.8% manganese, 5.3% aluminum, 1.8% silicon, 1.1% iron,0.8% lead, residual zinc and unavoidable impurities. Having propertiessimilar to those of alloy 2 is an alloy with 65.6% copper, 7.8%manganese, 5.3% aluminum, 1.8% silicon, 1.1% iron, 0.5% lead, 0.1%nickel, 0.2% tin, residual zinc and unavoidable impurities. An alloywith 70.5% copper, 7.8% manganese, 5.3% aluminum, 1.8% silicon, 1.1%iron, 0.05% lead, 0.1% nickel, 0.2% tin, residual zinc and unavoidableimpurities shows properties that correspond to those of alloy 3.

1. A copper zinc alloy used as a material for a sliding bearing, whereinthe alloy comprises in percent by weight 59-73% copper, 2.7-8.5%manganese, 1.5-6.3% aluminum, 0.2-4% silicon, 0.2-3% iron, 0-2% lead,0-2% nickel, 0-0.4% tin, residual zinc and unavoidable impurities.
 2. Acopper zinc alloy as claimed in claim 1, wherein the alloy comprises68-72.5% copper, 5.8-8.5% manganese, 3.6-6.3% aluminum, 0.5-3.3%silicon, 0.2-2.5% iron, 0.2-1.9% lead, 0-1.5% nickel, 0-0.4% tin,residual zinc and unavoidable impurities.
 3. A copper zinc alloy asclaimed in claim 2, wherein the alloy comprises 68.9-71.4% copper,6.9-8.5% manganese, 4.3-6% aluminum, 1.1-2.6% silicon, 0.4-1.9% iron,0.3-1.6% lead, 0-0.8% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.
 4. A copper zinc alloy as claimed in claim 3, wherein thealloy comprises 69.5-70.5% copper, 7.4-8.1% manganese, 4.8-5.7%aluminum, 1.5-2.2% silicon, 0.8-1.4% iron, 0.4-1.2% lead, 0-0.3% nickel,0-0.4% tin, residual zinc and unavoidable impurities.
 5. A copper zincalloy as claimed in claim 3, wherein the alloy comprises 69.4-71.4%copper, 7.4-8.1% manganese, 4.8-5.7% aluminum, 1.7-2.2% silicon,0.8-1.4% iron, 0.4-1.2% lead, 0-0.3% nickel, 0-0.4% tin, residual zincand unavoidable impurities.
 6. A copper zinc alloy as claimed in claim5, wherein the alloy comprises more than 70 and up to 71.4% copper,7.4-8.1% manganese, 4.8-5.7% aluminum, 1.8-2.2% silicon, 0.8-1.4% iron,0.4-1.2% lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.
 7. A copper zinc alloy as claimed in claim 1, wherein thealloy comprises 63.5-67.5% copper, 6-8.5% manganese, 3.6-6.3% aluminum,0.5-3% silicon, 0.2-2.5% iron, 0.02-1.8% lead, 0-1.5% nickel, 0-0.4%tin, residual zinc and unavoidable impurities.
 8. A copper zinc alloy asclaimed in claim 7, wherein the alloy comprises 64.5-66.5% copper,6.9-8.5% manganese, 4.3-6% aluminum, 0.9-2.6% silicon, 0.4-1.9% iron,0.1-1.3% lead, 0-0.8% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.
 9. A copper zinc alloy as claimed in claim 8, wherein thealloy comprises 65.1-66% copper, 7.4-8.1% manganese, 4.8-5.7% aluminum,1.3-2% silicon, 0.8-1.4% iron, 0.2-0.9% lead, 0-0.3% nickel, 0-0.4% tin,residual zinc and unavoidable impurities.
 10. A copper zinc alloy asclaimed in claim 9, wherein the alloy comprises 65.1-66% copper,7.4-8.1% manganese, 4.8-5.7% aluminum, 1.7-2% silicon, 0.8-1.4% iron,0.2-0.9% lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.
 11. A copper zinc alloy as claimed in claim 10, wherein thealloy comprises 65.1-66% copper, 7.4-8.1% manganese, 4.8-5.7% aluminum,1.8-2% silicon, 0.8-1.4% iron, 0.2-0.9% lead, 0-0.3% nickel, 0-0.4% tin,residual zinc and unavoidable impurities.
 12. A copper zinc alloy asclaimed in claim 1, wherein the alloy comprises 68.3-72.7% copper,5.7-8.5% manganese, 3.6-6.3% aluminum, 0.5-3.3% silicon, 0.2-2.5% iron,0-0.1% lead, 0-1.5% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.
 13. A copper zinc alloy as claimed in claim 12, wherein thealloy comprises 69.4-71.6% copper, 6.9-8.5% manganese, 4.3-6% aluminum,1.1-2.6% silicon, 0.4-1.9% iron, 0-0.1% lead, 0-0.8% nickel, 0-0.4% tin,residual zinc and unavoidable impurities.
 14. A copper zinc alloy asclaimed in claim 13, wherein the alloy comprises 70-71% copper, 7.4-8.1%manganese, 4.8-5.7% aluminum, 1.5-2.2% silicon, 0.8-1.4% iron, 0-0.1%lead, 0-0.3% nickel, 0-0.4% tin, residual zinc and unavoidableimpurities.
 15. A copper zinc alloy as claimed in claim 13, wherein thealloy comprises 69.4-71.4% copper, 7.4-8.1% manganese, 4.8-5.7%aluminum, 1.7-2.2% silicon, 0.8-1.4% iron, 0-0.1% lead, 0-0.3% nickel,0-0.4% tin, residual zinc and unavoidable impurities.
 16. A copper zincalloy as claimed in claim 15, wherein the alloy comprises more than 70and up to 71.4% copper, 7.4-8.1% manganese, 4.8-5.7% aluminum, 1.8-2.2%silicon, 0.8-1.4% iron, 0-0.1% lead, 0-0.3% nickel, 0-0.4% tin, residualzinc and unavoidable impurities.
 17. A copper zinc alloy as claimed inclaim 1, wherein the alloy additionally comprises up to 0.1% of amaterial selected from the group consisting of at least one of theelements chromium, vanadium, titanium or zirconium with up to 0.1%.